The invention relates to a diaphragm bellows having a plurality of diaphragms with outer edges and inner edges, diaphragms that follow one another in the direction of the longitudinal center axis of the diaphragm bellows being welded together alternately in the region of their inner edges and in the region of their outer edges, the diaphragm bellows additionally having at least one guide part for guiding on the outer surface of a rod passing through an inner through-opening in the diaphragm bellows. Additionally, the invention relates to a diaphragm bellows having a plurality of diaphragms with outer edges and inner edges, diaphragms that follow one another in the direction of the longitudinal center axis of the diaphragm bellows being welded together alternately in the region of their inner edges and in the region of their outer edges, the diaphragm bellows additionally having at least one guide part for guiding on the inner surface of a tube surrounding the diaphragm bellows.
Diaphragm bellows are generally used as a flexible sealing element in order to separate different pressure regions in an application. Thus, diaphragm bellows are used for example for vacuum leadthroughs of vacuum valves, the diaphragm bellows enclosing the drive rod of the valve and separating the vacuum region from the atmosphere region when the valve is opened and closed. In addition to applications for vacuum leadthroughs for introducing movement into the vacuum, diaphragm bellows can be used for example as compensators for absorbing thermal expansions or assembly tolerances. A further application is, for example, in vibration decoupling in a vacuum system, for example between a vacuum pump and a measuring instrument.
Diaphragm bellows consist of diaphragms that are welded together alternately at their outer and inner edges. During production, first of all diaphragm pairs are welded together at their inner edges and subsequently the diaphragm pairs are arranged alongside one another in a row and are welded together at their outer edges. By way of such diaphragm bellows, travel in an axial and/or lateral and/or angular direction is possible.
In addition to diaphragm bellows, corrugated bellows are known, in which tubes are deformed in a bellows-like manner, with the result that movability is achieved. Specific configurations of corrugated bellows can be gathered for example from U.S. Pat. No. 4,650,160 A and GB 2 062 132 A.
When diaphragm bellows are used, pressure differences usually arise between the interior and the outer side of the diaphragm bellows, it being possible for the pressure inside the diaphragm bellows to be lower or higher than the pressure outside the diaphragm bellows. Due to such pressure differences (in particular when a higher pressure prevails inside the diaphragm bellows than outside the diaphragm bellows) and/or as a result of gravitational force, it is possible, due to the low side rigidity of the diaphragm bellows, for lateral buckling of the diaphragm bellows to occur to a greater or lesser extent when the diaphragm bellows is sufficiently long. For example, as a result, the diaphragm bellows can come to bear against a rod (e.g. drive rod of a vacuum valve), extending through the inner through-opening in the diaphragm bellows, in regions of the welds of the inner edges of the diaphragm. In the event of the rod moving, the inner edges of the diaphragm thus rub against the rod, and this can result in wear to the weld seams between the inner edges of the diaphragms, with the result that the strength of these weld seams can be impaired over time and leaks can occur.
Therefore, guide parts for guiding the diaphragm bellows in the central regions of its longitudinal extent have already been used. A diaphragm bellows of the type mentioned at the beginning can be gathered from US 2002/0175480 A1. This document discloses annular guide parts (=sliding rings) having outwardly protruding protuberances which project into the space between adjacent diaphragms of the diaphragm bellows and fix the guide part in a form-fitting manner with respect to movement in an axial direction of the diaphragm bellows. The inner edges of the two diaphragms, between which each sliding ring is retained, rest against the outer lateral surface of the sliding ring. In the compressed state of the diaphragm bellows, the inner edges of adjacent diaphragms are also arranged over the outer lateral surface of the sliding ring. A particular drawback with such sliding rings is that the diaphragms, between which each sliding ring is retained, cannot be placed against one another. The possible axial travel of the diaphragm bellows is reduced as a result. In addition, such sliding rings have a relatively large mass compared with the diaphragms, and as a result additional dynamic loads on the diaphragms can occur. In the state installed in the vertical direction, different expansion of the diaphragm bellows below and above each sliding ring also occurs as a result of the mass of the sliding rings, and this is amplified in the case of a plurality of sliding rings being used and likewise results in higher loads on the diaphragm bellows.
In the case of the diaphragm bellows known from CN 203 363 518 U, a solid support ring is welded in between two portions of the diaphragm bellows. Similar problems to those described above occur here.
JP 2013221596 A describes a bellows have guide members configured in a scissors-like manner. This is a complicated structure.
It is also known to use diaphragm bellows in implantable infusion pumps for dispensing a medicament. The medicament is located inside the diaphragm bellows, which is closed at its underside by a bottom and at its top side by a base plate of the infusion pump. By way of a pressure acting on the bottom, the diaphragm bellows is compressed and the medicament is dosed. In order to determine the remaining volume of the diaphragm bellows and thus the remaining quantity of medicament, use is made of electronic resonance circuits which comprise a coil in the bottom of the diaphragm bellows. In order to increase the sensitivity of a resonance circuit in order to determine the volume of the diaphragm bellows, an additional central plate of the diaphragm bellows is used in EP 2 177 792 A1, said central plate having at least one opening for the medicament to pass through. In order to fasten the central plate, use is made of a retaining ring having retaining arms which are arranged in a cross shape, which are connected together in a central connecting region, and by way of which the intermediate plate is welded. The retaining ring is located, in the region of its outer edge, between the outer edges of two diaphragms and is welded thereto. A guide that prevents lateral buckling of the diaphragm bellows is not necessary in such a device just because of the shortness of the diaphragm bellows.